Possible Clues:

• Each of its interior angles measures 135°
• Regular form over swindle catching mark
• Shape of Athens' Tower of the Winds
• Old court in the past primarily noted for many-sided shape?
• A month back, new plane shape
• Figure of old Charlie — with label attached
• Figure running to span court with ace shot
• Figure takes turn through broken-down Acton
• Circle somehow can't go into figure with straight sides
• Goo can't be plastered over the figure